1. Field of the Invention
The present invention relates to a trigger switch having a normal and reverse switching lever used in a brushless motor-mounted power tool or the like and, more specifically, to a trigger switch having waterproof, leak-proof, and corrosion-proof structures.
2. Prior Art
A “trigger switch” described in JP-A-2009-054540 for example is known as a trigger switch having a normal and reverse switching lever in the prior art. As shown in FIGS. 12, 13, and 14, the trigger switch has a configuration including a sliding operation unit 15 having a sliding contact point mechanism integrated in the interior of a main body formed into a box shape, and configured to transmit a sliding operation from an external trigger lever 11, and also including a case 12 opening on a side surface, a cover 14 configured to close an opening surface on the side surface of the case 12 and provided with a sliding circuit board 13 mounted on an inner side surface thereof, the trigger lever 11 which allows operation by a finger, and a switching operation unit 25 provided at an upper position of the case 12 and configured to switch the direction of rotation of a motor between a normal rotation and a reverse rotation.
The switching operation unit 25 includes a switching lever 26 stored in a switching lever storage chamber 22 provided at the upper position of the case 12, and the switching lever 26 includes a switching knob 28 formed at an end portion of an arm member 27 formed into a trapezoidal shape so as to project upward, a revolving shaft 29 rotatably provided at a substantially center position, a contact strip member 30 configured to allow a switching contact strip 31 formed of a conductive metallic member which generates switching signals to be mounted on a side surface at a rear end portion thereof, and a spring 32 and a support seat 33 provided at the rear end portion.
The switching lever storage chamber 22 is formed with a revolving shaft engaging hole 23 and the revolving shaft 29 of the switching lever 26 is engages thereto, so that the switching lever 26 is rotatably stored therein. The switching knob 28 including the arm member 27 is positioned out of the case 12, and the contact strip member 30 having the switching contact strip 31 mounted thereon is arranged in the interior of the storage chamber 22.
A speed control unit 44 is coupled to a sliding shaft 41 of the sliding operation unit 15, and the speed control unit 44 includes a rotation control sliding element 42 and a switch sliding element 43 moved in conjunction with the sliding shaft 41, and the sliding circuit board 13 having contact elements 45, 46, 47, and 48 which comes into resilient contact with the rotation control sliding element 42 and the switch sliding element 43.
The conventional trigger switch having a configuration as described above has a structure in which the switching lever 26 is arranged with the revolving shaft 29 engaged with the revolving shaft engaging hole 23 of the switching lever storage chamber 22. However, since any protective measure for entry of water from the outside is not taken at all, there is a problem such that water enters from around the revolving shaft 29 of the switching lever in association with a switching operation of the switching lever, and the entered water is propagated to contact elements disposed on a sliding circuit board, thereby causing an erroneous operation.
There is another problem in the prior art such that the contact element of the sliding circuit board has a configuration in which electrodes or upper portions of the electrodes are coated with resister for allowing movable contact strips (rotation control sliding element, switch sliding element) to slide thereon, and hence the entry of water causes leak between the electrodes, which accelerates occurrence of corrosion, thereby causing the erroneous operation.